Pipe coupling

ABSTRACT

The present invention relates to a pipe coupling for connection to a pipe end of a pipe made of polymer material and intended preferably for tap water or heating installations. The pipe coupling includes an inner sleeve intended for insertion into the pipe end and for abutment with the inner surface of said pipe end. The coupling further includes an outer sleeve intended for abutment with the outer surface of said pipe end. The outer sleeve is provided with a slot-like opening and means for adjusting the width of said opening. When the outer sleeve is in a tightened, adjusted state, the sleeve will be internally and externally cylindrical. A center axis through the outer cylindrical surface of the outer sleeve is spaced at a distance from a center axis through the inner cylindrical surface of the outer sleeve. In the tightened, adjusted state of the outer sleeve, the internal radius of said sleeve is smaller than the external radius of said pipe end.

The present application is the national stage under 35 U.S.C. 371 ofPCT/SE99/01151, filed Jun. 24, 1999.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a pipe coupling for connection to apipe end of a plastic pipe, said pipe preferably being used in tap wateror heating installations. The coupling includes an inner sleeve forinsertion into said pipe end into abutment with the inner surfacethereof, and an outer sleeve which is intended to lie in abutment withthe outer surface of said pipe end and which includes a slot-likeopening and means for adjusting the size of said opening.

BACKGROUND OF THE INVENTION

A metal pipe coupling for interconnecting cross-linked polyethylenepipes installed in hot and cold water systems and in central anddistrict heating pipe systems is known to the art from U.S. Pat. No.4,039,212. This pipe coupling is of the kind described in theintroduction and is available in various versions designed to handledifferent pipe pressures, However, because of successively stricterapproval standards ordained by the relevant authorities, decreeing thatthe coupling joint shall be stronger than the pipe itself, has meantthat these pipe couplings are unable to meet satisfactorily certain testrequirements, such as pullout tests, load tests and other functionaltests carried out in practice. A common drawback with these earlierknown versions is that the couplings do not exert an evenly distributedclamping force around the full periphery of the pipe, that the couplingscannot be adjusted uniformly to provide a tight and sealed join, andthat they require detailed fitting instructions and continuousmonitoring of the tightening force.

SUMMARY OF THE INVENTIVE CONCEPT

An object of the present invention is to provide a pipe coupling which,in one and the same version, can manage different pipe pressures, whichwill fulfill the load and function requirements applicable to thesetypes of couplings, which can be fitted easily and quickly, and whichdoes not require the use of large and special tools in order to fit thecoupling.

This object is achieved in accordance with the invention, with acoupling that has the features set forth in the accompanying claims,

BRIEF DESCRIPTION OF THE ATTACHED DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings, in which

FIG. 1 is an exploded view of one embodiment of an inventive pipecoupling;

FIGS. 2a-2 b illustrate the inner sleeve of FIG. 1, of which FiguresFIG. 2a is a side view partially in cross-section, and FIG. 2b is aperspective view partially in cross-section;

FIGS. 3a-3 c illustrate the outer sleeve of FIG. 1, of which FIGS. 3a-3b are different side views and FIG. 3c is a cross-sectional view;

FIG. 4 is a schematic side view of the outer sleeve and for reasons ofclarity illustrates the eccentricity in the sleeve in an exaggeratedfashion;

FIG. 5 is a perspective, partially cross-sectional view of the pipecoupling of FIG. 1 fitted to one end of a pipe; and

FIG. 6 is an enlarged axial cross-sectional view of the pipe couplingshown in FIG. 5.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 illustrates the component parts of the inventive coupling, thesecomponent parts including an inner sleeve 1, an outer sleeve 2, a screw3, a nut 4, a washer 5 and an O-ring 6.

The inner sleeve 1, which is shown in more detail in FIGS. 2a-2 b, ismanufactured from a suitable material in the present context, preferablyfrom a metallic material, although other materials may be suitable, suchas various polymer materials, for instance. Particularly suitable innersleeve materials are sand-moulded and cast brass alloys.

The inner sleeve 1 is designed for connection to another coupling partand shall also afford an effective gripping and sealing function againstthe formable and ductile pipe wall and shall be capable of being lockedto the outer sleeve. Accordingly, the inner sleeve includes a grippingand sealing part 8, a locking part 10, and a connecting part 12.

The gripping and sealing part 8 of the inner sleeve, against which theductile pipe wall is intended to abut, is provided with one orpreferably more gripping ridges 14. The gripping ridge or ridges 14includes/include a first side surface 16 which is slightly inclined soas to enable the pipe 20 to be fitted onto the inner sleeve 1 moreeasily, and a second side surface 18 which slopes abruptly to form anedge which provides an effective gripping and sealing function. Thegripping and sealing part 8 also includes a groove 22 for receiving theO-ring 6. The gripping and sealing part 8 of the inner sleeve isdesigned for coaction with the inner surface of the outer sleeve 2, asdescribed below in more detail with reference to FIGS. 5 and 6.

The locking part 10 on the inner sleeve 1 has an abutment edge 24 forabutment With the end 21 of the pipe fitted onto said sleeve. Thelocking part 10 also includes a circular locking groove 26 for coactionwith the outer sleeve 2 in a manner to fixate and lock said sleeve, asdescribed in more detail herebelow. The locking part 10 may have anouter octahedral shape or some other shape which will enable it to begripped by a suitable tool.

The connection part 12 of the inner sleeve may be constructed indifferent ways, all in accordance with requirements, although it willinclude conveniently a conventional thread 28 for screw connection withanother coupling part (not shown).

The outer sleeve 2 is shown in more detail in FIGS. 3a-3 c, and alsoschematically in FIG. 4. The outer sleeve is made from a materialsuitable for the purpose intended, preferably from a metallic material,such as a bronze alloy, although other materials are also conceivable inthis context, such as polymer materials, for instance.

The outer sleeve 2 is constructed so as to enable it to exert a clampingforce on the outside of the pipe and so that it can be locked to theinner sleeve 1 in the pull direction. The outer sleeve 2 comprisesgenerally a clamping sleeve 30 that has a slot-like opening 34 and a jaw32 on each side of said opening 34. As will best be seen from FIG. 3c,the inner surface of the sleeve intended for abutment with the outsideof the pipe 20 includes abutment grooves 36. The jaws 32 includethrough-penetrating holes 38 (see also FIG. 1) through which the screw 3passes. Arranged on one end-wall part 39 of the clamping sleeve 30 aretwo mutually opposing, part-circular locking shoulders 40 which areintended for coaction with the inner sleeve 1, as described in moredetail below. The slot-like opening 34 includes a centrally arrangedcircular opening 42.

FIG. 4 is a schematic side view of the other end-wall part of the outersleeve 2, and includes an exaggerated illustration of this end-wall partwith the intention of illustrating the eccentric design of the clampingsleeve 30 more clearly. The outer sleeve 2 has a cylindrical outersurface 44 of radius A with a centre axis that passes through the pointX, and a cylindrical inner surface 46 of radius B, with a centre axisthat passes through the point Y. As will be seen from FIG. 4, the centreaxis Y of the inner surface 46 of the clamping sleeve is offset througha distance D in relation to the centre axis X of the outer surface 44 ofsaid clamping sleeve. The clamping sleeve 30 is thus constructedeccentrically and has a varying wall thickness Z which is greatest atthe side opposite to said slot-like opening 34 and smallest at saidslot-like opening. The distance D is about 0.5 mm in the illustratedcase.

When manufacturing the outer sleeve 2, the inner surface 46 of saidsleeve is first machined in a lathe to a measurement which correspondsto the diameter of the sleeve when the slot-like opening is fullyclosed, i.e. to a radius B that is smaller than the outer measurement ofthe pipe 20, i.e. smaller than the radius C (see FIG. 5). The slot-likeopening 34 is then, and only then, cut into the sleeve. When theslot-like opening is fully closed, the measurement of the inner surface46 will preferably be about 1-3.5 mm smaller than the outer diameter ofthe pipe, which means that the outer sleeve must be widened forcibly inorder to enable it to be fitted over the end of the pipe.

FIGS. 5 and 6 show the inventive pipe coupling fitted to one end of apipe 20. A first step in fitting the coupling to the pipe, as shown inFIG. 5 or FIG. 6, entails fitting the outer sleeve 2 onto the pipe 20 bywidening the slot-like opening 34 in said sleeve, primarily to an extentsufficient to be able to push the sleeve onto the end of the pipe andsecondarily to an extent such that the locking shoulders 40 will passfree when the inner sleeve is inserted into said pipe end, this wideningof the slot-like opening 34 being achieved with a tool inserted into thelocking-gap opening 42. The head of the screw 3 has a size which enablesit to be used to hold the slot-like opening 34 in an appropriatelywidened state to this end. At this moment in time, the end-wall part 39carrying the locking shoulders 40 shall face away from the pipe 20, asshown in FIG. 5. The eccentricity of the outer sleeve enables theslot-like opening 34 to be easily widened.

In a second step, the inner sleeve 1 is fitted into the end of the pipe,by pushing the gripping and sealing part 8 of the inner sleeve, saidpart carrying the O-ring 6 seated in groove 22, into the pipe end 20 sothat the edge 21 of said pipe will lie in abutment with the abutmentedge 24 on the locking part 10. The pipe 20 slides relatively smoothlyover the slightly inclined side surfaces 16 on the gripping ridges 14.

In a third step, the outer sleeve 2 is pushed on the pipe 20 to aposition in which the locking shoulders 40 Will snap into the lockinggroove 26 in the inner sleeve 1 when the forcibly widened slot-likeopening is allowed to return to its original state. The outer sleeve 2is therewith secured in relation to the inner sleeve 1 and the pipe end20.

The limited peripheral extension of the locking shoulders 40 and theirdistance from the slot-like opening 34 means that the slot-like openingneed only be widened to a limited extent in order to fit the outersleeve 2 onto the pipe end. In respect of those pipe sizes that arerelevant in the present context, which may vary between 25-110 mm, theslot-like opening will need only be widened to between about 6-19 mmfrom a width of about 2 mm in its unaffected state.

In the last step of fitting the outer sleeve, the sleeve is tightenedagainst the pipe 20 by inserting the screw 3 through the holes 38 andthe washer 5 and screwing the nut 4 onto the screw and slowly tighteningthe screw until the jaws 32 are in abutment with one another and theslot-like opening is closed. No complicated mounting instructions or theuse of complicated tools, such as torque wrenches, are required, sinceit is only necessary to tighten the nut and screw joint until theslot-like opening is fully closed, As before mentioned, the outer sleeveis machined to an inner diameter which corresponds to the diameter ofthe sleeve when in its tightened state, which means that the sleeve Willbe essentially cylindrical when tightened. This is made possible sincethe outer sleeve need only be widened to a limited extent when fittingthe sleeve, and by virtue of the eccentricity in the clamping sleevecreasing of the wall of the clamping sleeve is prevented when adjustingthe slot-like opening, This results in a uniformly distributed clampingforce and thus in a clamping force which is equally as great around theentire periphery of the pipe.

As will be seen from FIG. 6 (and also from FIG. 5), the inner sleeve 1,and its gripping ridges 14 in particular, abuts the inner surface of thepipe 20, and the outer sleeve 2, and its abutment grooves 36 inparticular, abuts the outer surface of the pipe 20. In the fixatedposition of the outer sleeve 2 relative to the pipe 20 and the innersleeve 1, as shown in FIG. 6, the gripping ridges 14 on the inner sleevewill abut with and press against the pipe between the grooves 36 on theouter sleeve, said ridges pressing against the pipe wall essentiallycentrally between the grooves 36. As the outer sleeve is tightened, thepipe material is pressed against the profiled gripping ridges 14 and istherewith shaped to the contours of said profiled ridges. This resultsin a very effective sealing and locking function that fulfils allprevailing standards and functional requirements relating to suchcouplings.

It will be noted that the aforedescribed preferred embodiment of theinvention is only a non-limiting example and that the invention can bevaried in many ways within the scope of the following claims. Forinstance, although the size of the slot-like opening in the preferredembodiment is given as being about 2 mm, it will be understood that thisopening may be both narrower and wider within the scope of theinvention, preferably between 0-10 mm, and that the slot width can bevaried in accordance with the size of the pipe involved. Furthermore,although the eccentricity in the clamping sleeve of the illustratedembodiment has been given as about 0.5 mm, it will be understood thatthis distance is only an example and that the distance D may be eithersmaller or greater, for instance between 0.1-5.0 mm and may also varyfurther depending on the size of the pipe concerned. The number ofgripping ridges and the number of abutment grooves can also vary and thegripping ridges and the grooves may both have a shape different to thatillustrated, As before mentioned, the inventive pipe couplings areintended for use in water-carrying conduit systems. It will beunderstood, however, that they can also be used in conduit systems forconducting other substances, such as gas or petroleum, for instance.

What is claimed is:
 1. A pipe coupling for connection to a pipe end of apipe made of polymer material, comprising an inner sleeve (1) which isintended for insertion into the pipe end (20) and for abutment with theinner surface of said pipe end, an outer sleeve (2) separated from theinner sleeve (1) which is intended for abutment with the outer surfaceof said pipe end (20) and which includes a slot opening (34), and means(3, 4, 5, 32) for adjusting said opening (34), characterized in theouter sleeve (2) is cylindrical internally and externally when theslot-like opening (34) is fully closed, that the slot-like opening (34)is fully closed when the outer sleeve (2) is in a first, unaffectedstate as well as when the outer sleeve (2) is in a tightened adjustedstate on the pipe end (20), that the internal radius (B) of said outersleeve (2) in said first, unaffected state being smaller than theexternal radius (C) of said pipe end (20), that a center axis (X)through the outer cylindrical surface (44) of the outer sleeve (2) isspaced at a distance (D) from a center axis (Y) through the innercylindrical surface (46) of the outer sleeve (2), that the inner sleeve(1) and the outer sleeve (2) are constructed so that they can be lockedto each other, and that the outer sleeve (2) and the slot-like opening(34) are adapted to be widened forcibly from said first, unaffectedstate such that the outer sleeve (2) may be fitted over said pipe end(20) and said inner sleeve (1).
 2. A pipe coupling according to claim 1,characterized in that the outer sleeve (2) includes one or more lockingshoulders (40) intended for coaction with a locking groove (26) in thesleeve (1) for fixating the outer sleeve (2) in relation to the innersleeve (1).
 3. A pipe coupling according to claim 2, characterized inthat said outer sleeve (2) is widened forcibly, primarily to an extentsufficient to be able to push the outer sleeve (2) onto the pipe end(20) and secondarily to an extent such that the locking shoulders (40)will pass free when the inner sleeve (1) is inserted into the pipe end(20).
 4. A pipe coupling according to claim 3, characterized in that thelocking shoulders (40) are disposed on the outer sleeve (2) at adistance from a plane that passes through the slot opening (34) in theouter sleeve.
 5. A pipe coupling according to claim 4, characterized inthat two mutually opposing locking shoulders (40) are provided on oneend-wall (39) of the outer sleeve at the greatest possible distance fromsaid plane passing through the slot opening (34) in the outer sleeve,each locking shoulder extending about ¼ of the circumference of theouter sleeve (2).
 6. A pipe coupling according to claim 1, characterizedin that said distance (D) is about 0.5 mm.
 7. A pipe coupling accordingto claim 1, characterized in that the slot opening (34) is completelyclosed in a tightened, adjusted state.
 8. A pipe coupling according toclaim 1, characterized in that the inner sleeve includes a gripping part(8) which is intended for insertion into the pipe end (20) and forabutment with the inner surface of said pipe end, and which carries oneor more gripping ridges (14).
 9. A pipe coupling according to claim 8,characterized in that when seen in the direction of insertion of theinner sleeve (1) into the pipe end (20), the gripping ridges (14) have aslightly sloping first side surface (16) and an opening, abruptlysloping second side surface (18).
 10. A pipe coupling according to claim8, characterized in that the outer sleeve (2) includes abutment grooves(36) that abut the outer surface of the pipe end (20) between saidgripping ridges (14).
 11. A pipe coupling according to claim 1,characterized in that said opening-adjusting means (3, 4, 5, 32)includes a jaw (32) on each side of the slot opening (34) and on theoutside of the outer sleeve, each jaw (32) having a through-penetratinghole (38) for receiving a screw (3) which as it is tightened causes thejaws (32) to be brought together and therewith close the opening (34).